Japanese macaque encephalomyelitis (JME) is a spontaneous inflammatory demyelinating disease occurring a colony of Japanese macaques. This JM colony was established in 1965 and no cases of JME occurred until 1986. Since 1986, 57 JMs spontaneously developed a disease characterized clinically by paresis or weakness of one or more limbs, unsteadiness of gait, or weakness of eye movements. Most affected animals were humanely euthanised during their initial episode. However, three recovered, later relapsed, and were then euthanised. MRI of 8 cases of JME revealed multiple gadolinium-enhancing (inflamed) lesions in the white matter of the brain and cervical spinal cord. The pathology contained multiple plaque-like demyelinated lesions of varying ages, including acute and chronic, active demyelinating lesions with macrophages (scavenger cells) and lymphocytic infiltrates around veins, and chronic, inactive demyelinated lesions. A previously undescribed gamma-herpesvirus was cultured from acute JME white matter lesions. Cases of JME continue to affect 1% to 3% of the colony per year. Interpretation: JME is a unique spontaneous disease in a nonhuman primate that has similarities with multiple sclerosis (MS) and is associated with a novel simian herpesvirus.

"One of the criteria for causation is reasoning by analogy. A spontaneous relapsing MS-like disease in a non-human primate with MRI and pathological features similar to MS ticks this box. I am still in the camp that thinks MS is due to an infection; EBV. Interestingly, EBV is a human gamma herpesvirus. Any supporters out there?"